1. Field of the Invention
The present invention pertains generally to the propulsion and steering of watercraft, and more particularly to a steerable propeller assembly applicable to such craft powered by conventional inboard mounted engines driving a straight line drive propeller shaft.
2. Description of the Prior Art.
Conventional inboard straight line drive powered boats are driven by means of a propeller affixed to the end of a rigidly mounted propeller shaft extending toward the stern of the vessel. Steering of the vessel is accomplished by a rudder disposed in the water at the rear thereof which is pivoted to an appropriate angular position so that water moving therepast provides a lateral thrust component causing the rear of the vessel to be displaced laterally In order to provide this steering thrust the rudder must, of course, be moving relative to the water, that is, the water must be moving along and past the rudder surfaces, due either to movement of the boat through the water or movement of water past the rudder by the propeller. Thus, while steering is readily accomplished at relatively high speeds, the rudder has very limited effectiveness at low speeds such as those necessary in maneuvering in and out of docking spaces and in harbor and marina areas. Due to the great increase in the number of boats in use in recent years, harbors and marinas have become increasingly congested, and maneuvering within such areas has become more difficult.
Watercraft powered by outboard engines and stern power out-drive units, the so-called "L" and "Z" drive units, respectively, are much more maneuverable than conventional inboard straight line drive powered vessels. The propellers of such craft can be swung in an arc to either side of the center line of the vessel to provide a component of direct lateral thrust to the stern of the craft. The thrust will thus swing the stern around without the necessity for linear movement of the craft through the water.
The merits of steerable propellers in guiding conventional inboard straight line drive powered watercraft are well recognized, and efforts have long been directed toward providing such devices which will function satisfactorily. U.S. Pat. No. 10,790, issued Apr. 18, 1854, discloses one early effort wherein a propeller and rudder are so mounted as to be pivotable. Steerable propeller arrangements are likewise disclosed in U.S. Pat. Nos. 135,404, issued Feb. 4. 1873; 189,603, issued Apr. 12, 1877; 571,127, issued Nov. 10, 1896; 2,398,033, issued Apr. 9, 1946; and 4,310,319, issued Jan. 12. 1982 While the advantages of having the ability to pivot or swing the axis of rotation of propellers have long been recognized, none of the mechanisms proposed thus far for use with inboard straight line drive systems has proven entirely satisfactory for that purpose. Thus, there remains a need for a mechanism which is relatively simple and inexpensive to manufacture, can be readily installed on both new and existing vessels, and is durable and relatively maintenance free.